Landowners are liable for damage caused by channeling surface waters onto their neighbor's property. If you sue within two years after the channeling started, you do not need to establish that your neighbor did it "maliciously," or even negligently. In Washington, there is "strict liability" for channeling water in the manner that you are describing, meaning that it doesn't matter whether your neighbor acted carelessly or intentionally. My firm handles many cases like this and I would be happy to discuss this matter with you at no charge for an initial consultation.
There are duties neighbor have to each other which includes to not cause harm to another's properties, so it does appear that you have a basis for the cause of action.
Do you have homeowner's insurance? That could cover the damage done to your home. However, if you cannot communicate with your neighbors to get them to stop diverting the rain water and flooding your property, it will continue happening until you get a court order. Consult with an attorney as soon as possible.